Syfy's upcoming Superman prequel, "Krypton," has added Paula Malcolmson to the cast as a guest star. The "Ray Donovan" and "Deadwood" actress will play Charys, the matriarch of the once mighty, now ostracized House of El.

The prequel centers on Superman's grandfather, Seg-El (Cameron Cuffe), as a young man. He fights to redeem his family from shame and save his world from chaos. Charys, his mother, will help him navigate the dangers of their home, Kandor City, which is in revolt.

Also joining the cast as a series regular is Blake Ritson ("Da Vinci's Demons"). He'll play Brainiac, a highly intelligent, parasitic, hyper-advanced alien android who goes on to become one of Superman's toughest foes.

Malcolmson recently departed Showtime's "Ray Donovan" after the death of her character. "Krypton" also stars Georgina Campbell, Ian McElhinney, Elliot Cowan, Ann Ogbomo, Rasmus Hardiker, Wallis Day,and Aaron Pierre. It is set to premiere in 2018.